This error has been from the day I first installed a clean install of FC4. It has not bothered me, as I don't use the root profile, but I thought I might as well report the error now.
In root only, not for other users, the following error message appears when logging in:
"Sound server informational message: Error while initializing the sound driver: device: default can't be opened for playback (Invalid argument) The sound server will continue, using the null output device."
For other users, the sound server works fine.
I am using kde-redhat for FC4 on a clean installation of FC4.